50psi Compression on my 302cid :(
Very Shy M
I checked my Compression today on my 66 stang and got 50 psi on average. I
had one cylinder give me 56psi. I really don't know what kind of
compression I am supposed to get with my setup. I have a 302cid from a 83
or 84 Ford LTD on my 66 Mustang. It has a Holley a 4 barrol 650CFM w/
Vacume Secondaries, Windsor Heads, Edelbrock Performer RPM Manifold and
Cam set along with Edelbrock Sure Seat Springs, and 1.6 Adjustable Roller
Rockers. The engine used to run fine with the stock stuff (2 barrol
manifold/Carb/exhaust from 66). I am still running the old single exhaust
from the 66. Right now the car really boggs off the line, I probably had
the same performance when I had the old engine with the 2 barrol manifold
on it. Right now what is happening is at 1200RPM I am getting poping back
in the carburator. I kind of see gas spit out of it when this happens.
I've tried advancing and retarding the timing, and nothing happens. I
think started having these problems when I rebuilt the carburator, but I
don't know why that is. The car seems to be getting good spark and a good
supply of gas. I am maintaining about 5psi in the gas line. Someone told
me the main venturi's might be leaning out or "the mains are maxing out"
as he put it, and it seems right because I get the same kind of poping at
lower RPM's as the car begins to die when I make the car starve for gas by
turning off the fuel pump. Could I have a bad Power Valve in my
carburator(poping in the carburator)? Could I have Jumped a tooth on my
Timing set(50psi)?
Thanks for any help in advance,
Dennis Espinoza
Owner of one slow 66 right now that runs real shitty. :(
mbu...@access.k12.wv.us
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Sounds like you either jumped time, or have bent valves.
I'm surprised it even runs with 50psi cranking pressure. It
should have around 130psi or more. Did you check the piston
to valve clearance? If not you could be bleeding off pressure
through valves that are slightly bent... The only other obvious
problem I can think of would be a jumped timing chain... but
didn't you just put in a new one along with your other new parts?
Regardless, with that size camshaft and the dished pistons that
come in those engines, I would suggest an earlier set of heads
that have smaller combustion chambers to build some more cylinder
pressure when you get it straightened out. Go for a set of 289
heads... install hardened exhaust seats and port them a bit...
especialy in the valve bowls and exhaust ports.
Mike Burch
66 mustang, 4-speed streeter
6.74 @ 101.6